@nanocollective/nanocoder/dist/hooks/useContextPercentage.js

A local-first CLI coding agent that brings the power of agentic coding tools like Claude Code and Gemini CLI to local models or controlled APIs like OpenRouter

import { useEffect, useRef } from 'react';
import { getModelContextLimit } from '../models/index.js';
import { calculateTokenBreakdown, calculateToolDefinitionsTokens, } from '../usage/calculator.js';
import { processPromptTemplate } from '../utils/prompt-processor.js';
export function useContextPercentage({ currentModel, messages, tokenizer, getMessageTokens, toolManager, streamingTokenCount, contextLimit, setContextPercentUsed, setContextLimit, }) {
    const contextLimitRef = useRef(null);
    const lastModelRef = useRef('');
    // Effect 1: Resolve context limit when model changes
    useEffect(() => {
        if (!currentModel) {
            contextLimitRef.current = null;
            setContextLimit(null);
            setContextPercentUsed(null);
            return;
        }
        if (currentModel === lastModelRef.current)
            return;
        lastModelRef.current = currentModel;
        let cancelled = false;
        void getModelContextLimit(currentModel).then(limit => {
            if (cancelled)
                return;
            contextLimitRef.current = limit;
            setContextLimit(limit);
            if (!limit) {
                setContextPercentUsed(null);
            }
        });
        return () => {
            cancelled = true;
        };
    }, [currentModel, setContextLimit, setContextPercentUsed]);
    // Effect 2: Recalculate percentage when messages, streaming tokens, or context limit change
    useEffect(() => {
        const limit = contextLimitRef.current;
        if (!limit) {
            setContextPercentUsed(null);
            return;
        }
        // Include system prompt in calculation (same as /usage command)
        const systemPrompt = processPromptTemplate();
        const systemMessage = {
            role: 'system',
            content: systemPrompt,
        };
        const breakdown = calculateTokenBreakdown([systemMessage, ...messages], tokenizer, (message) => {
            // System message won't be in the cache, use tokenizer directly
            if (message.role === 'system') {
                return tokenizer.countTokens(message);
            }
            return getMessageTokens(message);
        });
        // Include tool definition overhead (same as /usage command)
        const toolDefTokens = toolManager
            ? calculateToolDefinitionsTokens(Object.keys(toolManager.getToolRegistry()).length)
            : 0;
        const total = breakdown.total + toolDefTokens + streamingTokenCount;
        const percent = Math.round((total / limit) * 100);
        setContextPercentUsed(percent);
        // contextLimit is included to re-trigger calculation after async limit resolution
        // eslint-disable-next-line react-hooks/exhaustive-deps
    }, [
        messages,
        tokenizer,
        getMessageTokens,
        toolManager,
        streamingTokenCount,
        setContextPercentUsed,
    ]);
}
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